Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$157.65	6.470%	$167.85	$167.85	$167.85	$167.90
Purchase #2	$150.58	5.854%	$159.395	$159.40	$159.40	$159.40
Purchase #3	$166.62	11.649%	$186.0296	$186.03	$186.05	$186.00
Purchase #4	$48.87	7.372%	$52.4727	$52.47	$52.45	$52.50
Purchase #5	$105.52	5.545%	$111.3711	$111.37	$111.35	$111.40
Purchase #6	$142.64	11.436%	$158.9523	$158.95	$158.95	$159.00
Purchase #7	$101.90	13.446%	$115.6015	$115.60	$115.60	$115.60
7 purchase totals =	$873.78		$951.6722	$951.67	$951.65	$951.80